Torque sensor system including an elliptically magnetized shaft

• US 7,363,827 B2
• Filed: 11/09/2005
• Issued: 04/29/2008
• Est. Priority Date: 10/21/2005
• Status: Active Grant

• Current Assignee: Stoneridge Control Devices, Inc. (Stoneridge Incorporated)
• Original Assignee: Stoneridge Control Devices, Inc. (Stoneridge Incorporated)
• Inventors: Hedayat, Kayvan, Poirier, Norman
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): DUNLAP, JONATHAN M
• Application Number:
  US11/270,049
• Publication Number:
  US 20070113683A1
• Time in Patent Office: 902 Days
• Field of Search: 738/623.33, 738/623.31, 297/19, 148100-104, 148/108, 75/101.4
• US Class Current: 73/862.333
• CPC Class Codes: G01L 3/102 involving magnetostrictive means magnetostrictive sensors H10N35/101

Abstract

A torque sensor includes a shaft and a magnetic sensor. The shaft may have at least one active region having an elliptical magnetization. The magnetic sensor may be configured to sense a magnetic field about the shaft, where the magnetic field is representative of a torque applied to the shaft. The elliptical magnetization may have a nonzero axial component directed along a center line axis of said shaft at zero torque.

Claims

1. A torque sensor comprising:

a shaft having at least one active region, said at least one active region having an elliptical magnetization; and

a magnetic sensor configured to sense a magnetic field about said shaft, said magnetic field being representative of a torque applied to said shaft,

wherein said elliptical magnetization is induced by current driven between a pair of magnetizing clamps, said pair of magnetizing clamps oriented in parallel with each other and further oriented at an oblique angle with respect to a center line axis of said shaft, wherein said elliptical magnetization has a nonzero axial component along a center line axis of said shaft at zero torque, and wherein said nonzero axial component at zero torque is at least partially dependent on a value of said oblique angle.

2. The torque sensor of claim 1, wherein said magnetic sensor is configured to sense said nonzero axial component at zero torque.

3. The torque sensor of claim 1, wherein nonzero axial component changes as said torque is applied to said shaft.

4. The torque sensor of claim 1, wherein said magnetic field sensed by said magnetic sensor comprises alternating magnetic polarities as said shaft is rotated and said magnetic sensor provides a sinusoidal signal having an amplitude representative of said torque applied to said shaft.

5. The torque sensor of claim 4, wherein a frequency of said sinusoidal signal is representative of a speed of said shaft.

6. A method of monitoring a torque applied to a shaft comprising:

magnetizing an active region of said shaft to have an elliptical magnetization, said magnetizing comprising;

orientating a pair of magnetizing clamps about said shaft, said pair of magnetizing clamps oriented in parallel with each other and at an oblique angle with respect to a center line axis of said shaft, and

driving a current between said pair of magnetizing clamps; and

monitoring a magnetic field about said shaft, said magnetic field being representative of said torque applied to said shaft.

7. The method of claim 6, wherein said elliptical magnetization has a nonzero axial component directed along a center line axis of said shaft at zero torque.

8. The method of claim 6, wherein said oblique angle is between about 10 degrees and 80 degrees.

9. The method of claim 6, wherein said elliptical magnetization has an axial component along a center line axis of said shaft at zero torque, and wherein said axial component changes as said torque is applied to said shaft.

10. The method of claim 6, wherein said monitored magnetic field comprises alternating magnetic polarities as said shaft is rotated and wherein said method further comprises providing a sinusoidal signal having an amplitude representative of said torque applied to said shaft.

11. The method of claim 10, wherein a frequency of said sinusoidal signal is representative of a speed of said shaft.